 /*******************************************************************************
  * Copyright (c) 2006, 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.core.databinding.observable.value;

 import org.eclipse.core.databinding.observable.IObservablesListener;
 import org.eclipse.core.databinding.observable.ObservableEvent;

 /**
  * Value changing event describing a pending change of an
  * {@link IObservableValue} object's current value. Listeners can veto the
  * pending change by setting {@link #veto} to <code>true</code>.
  *
  * @since 1.0
  *
  */
 public class ValueChangingEvent extends ObservableEvent {

     /**
      *
      */
     private static final long serialVersionUID = 2305345286999701156L;

     static final Object TYPE = new Object ();

     /**
      * Description of the change to the source observable value. Listeners must
      * not change this field.
      */
     public ValueDiff diff;

     /**
      * Flag for vetoing this change. Default value is <code>false</code>, can
      * be set to <code>true</code> by listeners to veto this change.
      */
     public boolean veto = false;

     /**
      * Creates a new value changing event.
      *
      * @param source
      * the source observable value
      * @param diff
      * the value change
      */
     public ValueChangingEvent(IObservableValue source, ValueDiff diff) {
         super(source);
         this.diff = diff;
     }

     /**
      * @return the observable value from which this event originated
      */
     public IObservableValue getObservableValue() {
         return (IObservableValue) source;
     }

     protected void dispatch(IObservablesListener listener) {
         ((IValueChangingListener) listener).handleValueChanging(this);
     }

     protected Object getListenerType() {
         return TYPE;
     }

 }

